Electronic apparatuses such as a mobile telephone or a personal computer are composed by combining many electronic parts such as various integrated circuits, a resistor, and a capacitor. Each of electronic apparatuses mounts thereon an oscillator having a clock frequency according to its specifications. Each of plural housed electronic components is driven according to a clock signal, thereby achieving operational characteristics complying with the specifications.
In a communication apparatus which performs communications with an external apparatus, data carrier frequencies are different according to a country in which the device is used or the type of external apparatus to be connected. Therefore, a preferred clock frequency may depend upon a network condition on a client side even in the case of the communication apparatuses of the same type. In view of this, there are prepared plural versions mounting plural oscillators having clock frequencies different from each other in one type of communication apparatus; or plural oscillators having clock frequencies different from each other are mounted in one communication apparatus, and then, only an oscillator having a clock frequency suitable for a network condition is set to be effectively available on a client side, thus raising a problem of unnecessary cost.
In regard to this, a programmable oscillator whose oscillation frequency may be set by a user has been used in recent years (see, for example, Japanese Laid-open Patent Publication Nos. 2005-276179, 2001-320275, 11-55118, and 2000-341119). It is conceivable to mount such a programmable oscillator on a communication apparatus. The programmable oscillator is mounted on the communication apparatus, and a clock frequency according to a network condition on a client side is set, so that it is possible to save time and effort in preparing communication apparatuses of plural versions or mounting plural oscillators inside of one communication apparatus, thus reducing fabrication cost.
However, in delivering the communication apparatus to a client, it is necessary for an engineer of a manufacturer of the communication apparatus to visit to the client, to determine a clock frequency in consideration of a network condition or the like, and to set the clock frequency for the programmable oscillator. In addition, every time the use environment of the communication apparatus is changed, an engineer needs to determine and reset the clock frequency, thereby raising a problem of cumbersome maintenance.
Such a problem is not limited to only the communication apparatus but generally arises in the field of the electronic apparatus which inputs and/or outputs a signal to and/or from an external apparatus.
In view of the foregoing, an object of the present invention is to provide an electronic apparatus, a clock apparatus, and a clock control apparatus in which a clock frequency may be readily set.